When auto-tuning is enabled, CA IDMS begins to collect high water mark (HWM) information for the parameters being tuned. This information is collected on 24-hour intervals from the time the DC/UCF system is started. At the end of each interval, the statistics needed for tuning are updated and written to the AUTOTUNE member in SYSTRK and each HWM value is set to the current value of its associated parameter.
Statistical information is also collected at shutdown, but only if the system has been active for at least eight hours.
After five sets of statistics have been gathered and at the end of each interval thereafter, CA IDMS calculates a new value for each of the parameters being tuned. These values are used the next time the DC/UCF system is started after a normal shutdown. If the system is started after an abnormal termination, the parameter values from the previous execution are used. If you change the SYSGEN value of a tuned parameter, the new SYSGEN value is used the next time the system is started, and all historical information for the parameter is discarded.
New parameter values are recalculated at the end of each interval using the most recent HWM and information gathered from prior intervals. A smoothing algorithm is used so that abnormal conditions, such as runaway tasks, do not skew the results. Tuned values can both increase and decrease; however, they decrease more slowly than they increase.
You can use the DCMT DISPLAY AUTOTUNE command to see the current and new values for each of the tuned parameters and obtain graphs of HWM values over the last 32 time intervals.
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